An improvement of tilted AlN for shear and longitudinal acoustic wave

作者：Chung, Chen Jen; Chen, Ying Chung; Cheng, Chien Chuan; Kao, Kuo Sheng^*

来源：Applied Physics A-Materials Science & Processing, 2009, 94(2): 307-313.

DOI：10.1007/s00339-008-4793-7

This study investigates c-axis tilted aluminum nitride (AlN) piezoelectric films for the improvement of both shear and longitudinal acoustic wave resonances. Solidly-mounted resonator (SMR) structure is adopted for the applications of high frequency wireless communications and high sensitivity sensors. As to the piezoelectric layer, c-axis tilted AlN has the capability to excite the dual-mode resonances, namely, the longitudinal and shear mode resonances. In this study, SMR devices made with a seven-layer molybdenum/silicon dioxide (Mo/SiO2) Bragg reflector and the caxis tilted AlN are carried out. A conventional off-axis sputtering technique is applied to grow the tilted AlN.
The outcome frequency responses show dual resonant characteristics. However, the longitudinal resonance fades away with the AlN c-axis tilted angle, and the quality factor of the longitudinal resonance decreases. Consequently, we make an improvement by tilting the off-center substrates toward the sputtering source and successfully enhance the longitudinal resonance while preserving the shear resonance at the same time. Not only the shear resonance for the liquid-based sensing application, but also an outstanding longitudinal resonance could be obtained. The practicability of the dual-mode resonator is extended.

• 出版日期2009-2
• 单位中山大学